Light pulses of duration in the picosecond or femtosecond range, often referred to as “ultrashort” light pulses, are desired in a variety of applications, such as for example in the laser micromachining/processing and biomedical fields. Among other features, it can be advantageous for the optical sources emitting such light pulses to be flexible, allowing customization and easy tuning of parameters such as the pulse duration, repetition rate and spectral contents. The generation of light pulses “on-demand” can also be a desirable feature for some applications.
Various types of laser sources apt to produce ultrashort light pulses are known in the art. For example, mode-locked lasers can produce pulses as short as 10 fs. Their use in some contexts is however limited by their inherently fixed pulse repetition rate, typically in the MHz range. Mode-locked lasers may also lack the reliability required in several industrial applications. By contrast, Q-switch lasers are known to be very reliable as well as able to provide pulses of high peak power. Drawbacks of Q-switching technology however include limited adaptability in wavelength, low pulse repetition rates and minimum pulse durations around 10 ps. Also known in the art are gain-switched semiconductor lasers, providing relatively long pulses of around 50 to 100 ps. Such lasers can be operated on-demand, but the minimum pulse duration can vary from laser chip to laser chip, and the spectral contents cannot be well controlled.
Modulation of a light outputted by a seed laser diode can be a versatile laser pulse generation scheme. One or more phase or amplitude modulators can be used downstream of a pulsed or CW seed diode and operated to define or refine the temporal characteristics of the seed light. Advantageously, such systems can provide good control on both the temporal shape and spectral contents of the generated light pulses. Such configurations are however typically limited to generating light pulses of about 25-ps duration or longer.
In view of the above, there remains a need for flexible and versatile systems and method for generating ultrashort light pulses.